I've been having this problem for a while. Basically, whenever I restart, the harddrive won't detect. If I power down and then back on again, it fine, no problems. No new hardware, everything else works fine and always has. Maybe the connector pin from the reset button to the motherboard isn't in the proper position? Not life threatening, just kind of annoying! Any suggestions?
And also dust can be filled up on the connection ports and such things. Try to clean them before connect the wires and all the stuff.